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a name for a Japanese dragon or legendary serpent-like creature, which is aquatic or somehow related to water. Some commentators perceived it to have been a water deity.

At one level, mizuchi seems to have been the Japanese name for such a creature, but besides one mention in the ancient chronicle Nihon Shoki, and one Manyoshu poem, there is a dearth of information regarding the original mizuchi.

At another level, the name mizuchi (midzuchi) is the kun-yomi or Japanese equivalent name applied to several mythological creatures of the dragon kind in Chinese literature.

Agatamori battling mizuchi in the pool.
From Zenken kojitsu (1878)

Early references
The ancient chronicle Nihongi contains the earliest references to mizuchi. Under the 67th year of the reign of Emperor Nintoku (conventionally dated 379 A.D.), it is mentioned that in central Kibi Province, at a fork on Kawashima River (川嶋河, old name of Takahashi River (高梁川) in Okayama Prefecture), a great water serpent or dragon (大虬) dwelled and would breathe or spew out its venom, poisoning and killing many passersby.

A man named Agatamori (県守), ancestor of the Kasa-no-omi (笠臣) clan, came up to the pool of the river, and threw in three calabashes which floated to the surface of the water. He then challenged the beast, saying he would quit the spot if it could sink these gourds, but slay it if it failed. The beast transformed into a deer and tried unsuccessfully to sink them, whereby the man slew the monster. The record goes on to say: "..He further sought out the water-dragon's fellows. Now the tribe of all the water-dragons filled a cave in the bottom of the pool. He slew them every one, and the water of the river became changed to blood. Therefore that water was called the pool of Agatamori" (tr. Aston 1896:1,299).

Another entry under Nintoku (323 CE) records a somewhat connected cirumstance. The Mamuta dikes built along Yodo River kept getting breached. The Emperor then had an oracular dream, which prescribed two men, Kowa-kubi from Musashi Province and Koromo-no-ko from Kawachi Province to be sacrificed to the River God or Kawa-no-kami (河伯). One of the men, who resisted being sacrificed, employed the floating calabash and dared the River God to sink it as proof to show it was truly divine will that demanded him as sacrifice. A whirlwind came and tried, but the calabash just floated away, and thus he extricated himself from death using his wits. This entry mentions River God, but not the precise word mizuchi. Therefore, in spite of Aston who in another work discusses the River God (Kawa-no-kami) mentioned here and mizuchi in the same breath (Aston 1905:1, 150-151), one must caution against automatically equating one with the other.

De Visser concludes,
"From this passage we learn that in ancient times human sacrifices were made to the dragon-shaped river-gods." Foster (1998:1) suggests this is "perhaps the first documented appearance of the water spirit that would become known popularly in Japan as the kappa." In Japanese folklore the kappa is a water sprite often considered benignly mischievous, in contrast to the deadly dragon. However, the kappa can also be seen as sinister, reaching in and extracting the liver or the shirikodama from humans (see also #Name for kappa below).

In the Man'yōshū, Book 16, a tanka poem composed by Prince Sakaibe (境部王) reads:"虎尓乗 古屋乎越而 青淵尓 鮫龍取将来 劒刀毛我"
(Yoshimoto 1998), interpreted to mean, "Oh if I only had a tiger to ride to leap over the Old Shack, to the green pool to capture the mizuchi dragon,
and a (capable) sword (in hand)".
The Old Shack, Furuya, may actually signify a place name, with a possible double-entendre involved.

Folklorist study on mizuchi
- snip -

Name for kappa
Minakata also collected variants that sounded like mizuchi in local dialects, such as mizushi (Ishikawa prefecture), medochi (Iwate prefecture), mintsuchi (Hokkaido). Elsewhere, Asakawa Zenan (Essay, vol. 1, 1850) mentions medochi (Ehime prefecture) and mizushi (Fukui prefecture). However these all turned out to be local names for the kappa or "water imp". Minakata observed however that the kappa legend started out as tales of the nushi (den-masters of water) transforming into human-like forms and causing harm to humans, but that these origins had become forgotten.
Folklorists such as Yanagita and Junichiro Ishikawa inherit a similar view.

Minakata in this work has also collected local lore around Japan regarding aquatic snakes capable of killing humans. And he has made connection between these snakes and the lore around the kappa which has the reputation of extracting the shirikodama or a fabulous organ belonging to the human victim that the kappa is capable of yanking out through the anus. This connection seems to serve his conviction that the mizuchi though in later times identified with the kappa, originally referred to aquatic snakes.
Mizuchi as synonym for Chinese dragon names
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The medochi use human females to have them bear their children. When the child is born, the Medochi comes to claim his child. If the woman throws the baby into the water to kill it, Medochi takes the bones with him.

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Many people believe that early kokeshi wooden dolls were representations of girl children that were aborted or put to death after childbirth due to the inability to support a poor family of greater size.
Even the word, ko-keshi (ko o kesu 子を消す), can be loosely translated as "extinguished child" or
“a child wiped out”.

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One of Mr. Yanagita’s outstanding contributions to the etymology of the Japanese language is the theory advanced by him that such words as mizushi, which is used for kappa in Kaga and Noto provinces, medochi in Nambu and the Ainu mintsuchi, are all derived from mizuchi, which in its turn is a variation of mizu-tsuchi meaning a divine being in the water and having no connection originally with the Chinese ideograph chiao or ch’iu which is usually rendered into Japanese as m i z u h i , ) and being of the opinion that the kappa are water-gods who had degenerated into water-monsters, Mr. Yanagita says at the end of his article,

"In this reason, such instances as the kappa festival in Tosa when horses are tethered to stakes by the waterside may probably be considered as a sort of an old-age pension paid to the mixuchi, and such place-names as Senzoku-no-ike (” Feet-washiilg pond “) and Uma-arai-buchi (” Horse-washing pool “), as well as the name Koma-tsunagi-no matsu (”Horse-tethering pine “), given to certain pine trees in all parts of our country and the reason for which has so far remained unknown, are most likely the relics of yearly rites held in ancient times at which horses were offered to the water-god, and which in course of time came to be regarded by the agricultural population simply as a means of safeguarding their horses from evil throughout the year, the origin of the practice becoming completely forgotten. The custom, however, of offering the heads of oxen and horses to the water-god to pray for rain was long preserved.”

It may be difficult to find actual instances in Japan of oxen and horses being offered yearly to the water-god, but if we take into consideration the legends and customs in all parts of the Eurasian continent discussed in these pages, it becomes no longer possible to question Mr. Yanagita’s conclusion that such Japanese customs as the Nakoshi-matsuri and Ushi-no-yabuiri, or indeed the Japanese legend of the kappa trying to lure horses into the water, have their origin in the sacrifice of oxen and horses to the water-god in remote ages.”- source : japanesemythology.wordpress.com

There are a lot of legends about Kappa fighting the humans in the area of the Chikugo river 筑後川. But in the end the humans won and 九千坊河童 Kusengbo Kappa became the protector deity at this Suitengu Shrine.
So there are some prescriptions for the Shrine worshippers to prevent water accidents.

Before entering the water of a river you have to call out
"I am a heavenly messenger (mooshigo 申し子) sent from the Suitengu Shrine".
「水に入る前には水天宮の申し子だと唱える」

Other preventions from water accidents are :
- - not to eat mushrooms before entering the water
- - to have a bite from the rice offered at the Buddhist family altar 仏前飯

Kappa amulets of the shrine 河童面(かっぱめん)（箱・絵馬）
one mask comes in a box, the other on a votive tablet (ema).
They prevent evil influence and disasters. They must be hung in the demon-avoiding corner 鬼門 of the home.
Also 河童竹 and clay bells with the Kappa 河童鈴.

Shibaten しばてん / 芝天 otter and Kappa from Tosa
Along the rivers of Kochi lived a lot of kawauso 獺魚 otters, which legends often turned into a kappa called Shibaten, or revered it in his form of a river deity Enko 猿猴 .
Like the people of Tosa, the Shibaten likes sumo wrestling and always challenges people whom he meets on the road.
Nowadays clean natural rivers without concrete banks are seldom, so the Shibaten (and the river otter) is seen much less often.

Shibaten is usually depicted as childlike, of about 1 meter hight, with a lot of hair on the body.

新先生一代記

Maybe this river monster was once a Tengu and retained the part in the name of
ShibaTEN 芝天.SHIBA シバ can also relate to the famous dog race, Shiba ken 柴犬.

Hariko papermachee dolls of the Shibaten kappa were given to children to protect them from river accidents.

These two turtle character dolls are from a Japanese fable.
The bottom of the wood base to the tip of top of hair each measures approx. 6 1/2 - 7" tall. They have hand painted faces with side glancing eyes. The turtle with the light brown/titian hair is marked on the bottom of base: JAPAN in black ink and then has a store tag that reads: Futaba Doll Atelier Kochi. He has a small hole back of right leg.
The dark brown hair turtle has two brown stains by the right part of his mouth and one at the right side of his hair. He is marked: MADE IN JAPAN on bottom of his base.

shibaten シバテン / shiba tengu 柴天狗 Shiba Tengu, Shibatengu
Like a Kappa, he hangs around rivers, asks people to have a wrestling bout and begins to confuse their minds.
But he never goes into the river himself, so he is not a real Kappa.

In the village of 面河村 Omogo in the 上浮穴郡 Kamiukena district, there is a Shiba-Tengu. He is about 115 cm high and his nose is a bit smaller that that of a long-nosed Tengu. He is crazy about Sumo wrestling. If people pass along his river, he makes the sound of an ax cutting a tree and invents other deeds to scare people.
If people hear the sound of カーンカーン kaan-kaan and the falling down of a tree, they know the Shibaten is near.

At the slope ヒロイアゲの坂 Hiroiage no Saka on the mountain path up to the shrine 月山神社 Tsukiyama Jinja a bald priest came out and asked for a bout of Sumo wrestling. The priest was very strong and about to win, when the villager bit him in the shoulder. Suddenly the mountain made a huge sound and the priest changed in Shiba Tengu.

高知県幡多郡大月町月ヶ丘1443 / Tsukigaoka Saitsuno, Ōtsuki-chō, Hata-gun, Kōchi

During the 白鳳時代 Hakuho period (645 - 710) 役の行者（役小角） En no Gyoja found a sacred rock in the form of a mikkazuki 三日月 new moon and prayed there.
The rock is dedicated to the Shinto deity Uganomitama 倉稲魂命 Ukano Mitama.
Later 空海 弘法大師 Kukai Kobo Daishi passed here and prayed there for 23 days and nights.
In the Meiji period, the shrine was made into a temple, named 守月山月光院南照寺, with 勢至菩薩 Seishi Bosatsu as the Buddhist deity.

The rock used to be at a place called hime no i 媛の井 / 姫ノ井 "well of the princess" and moved with supernatural powers to its present location. Thus it got more and more spiritual power and people come to pray and make wishes.

Shibaten 芝天
If Shibaten comes for a bout of Sumo, he usually wins by throwing the human on the ground.
Sometimes humans try to impersonate Shibaten to enjoy some Sumo with others.
If people eat 鰌 Dojo loach alive, they will become able to see Shibaten.

- quoteKAPPA 河童 and SUIJIN 水神
The Kappa is one of many Suijin 水神 (water kami, water deities) in Japanese mythology.
Suijin are supernatural beings found in lakes, ponds, springs, wells, and irrigation waterways. They are often depicted as a snake, a dragon, an eel, a fish, a turtle, or a kappa. Many trace their origins back to earlier Chinese mythology, although Japan’s Kappa lore is largely indigenous.

The Suijin commonly possess magical powers, which can be used for either benevolent or malevolent purposes. For instance, the flesh-eating Kappa is mostly evil, but when captured, it will pledge to assist with farm work or to teach its captor the arts of setting bones and making medicines and salves.

One of the most curious Suijin in Japan manifests itself as the water-cleansing bacteria in sewage water (see Gabi Greve Mizu no Kamisama).
According to the Institute for Japanese Culture & Classics (Kokugakuin University) , women have played an important role in the history of Suijin worship in Japan. However, with the great influx of Korean and Chinese people into Japan starting around the 2nd century AD, and with the subsequent introduction of Buddhism in the 6th century, Japan’s many indigenous water kami began to slowly absorb attributes from these emigrants and from Buddhism. Not surprisingly, this ongoing mixture of traditions makes it difficult to identify the origins of these “syncretic” deities. This difficulty is compounded by the lack of Shintō artwork or written records prior to the 8th century. The most powerful, universal, and benevolent Suijin in Japan is known as Mizu no Kamisama 水の神様 (Goddess/God of Water).

The Kappa, however, is more accurately described as the Kawa no Kami 川の神 (River Deity), a term mentioned in the Nihon Shoki 日本書紀 (Chronicles of Japan), one of Japan's earliest official records, compiled around 720 AD. Some believe the Kappa, who didn’t appear as a popular icon until much later in the Edo Period (1615-1868), is none other than the river deity Kawa no Kami. Please see the Suijin Page for details on Japan’s Suijin traditions.

- Shintō Mythology
Some believe the Kappa is the “Kawa no Kami” 川の神 (lit. River Deity) mentioned in the Nihon Shoki 日本書紀 (Chronicles of Japan), one of Japan's earliest official records, compiled around 720 AD. Despite the Kappa’s seemingly ancient origin, the creature does not appear (to my knowledge) in texts and artwork of the medieval period.
In fact, the earliest illustration of the Kappa comes from the Wakan Sansaizue 和漢三才図会, a 105-volume encyclopedia complied around 1713.

Another image appeared in the illustrated four-volume Gazu Hyakkiyagyō 画図百鬼夜行 (Night Procession of One Hundred Demons). Kappa lore gained steadily in popularity throughout the Edo Period (1615-1868). We find mention of Kawatarō (Kawataro) 河太郎 in a serial called Kasshiyawa 甲子夜話, first appearing in 1821 and running until the death of the author in 1841.
We also find mention of the Kappa in the mid-Edo period document named Mimibukuro 耳嚢 (or 耳袋), a 10-volume document written by Negishi Yasumori 根岸鎮衛 (1737-1815). Translated in English as “Bag of Ears,” it is a collection of essays about then-prevailing religious and cultural beliefs.

天疫神社 Teneki Jinja / Tenyaku Jinja / Ten'eki Jinja
It was founded around 900 when a pestilence and illness during a drought were killing many.
The shrine was built with the help of the villagers on top of Mount Takatsuki 高杯山 - and indeed, the pestilence subsided.

The shrine soon became famous in all of Northern Kyushu.
In the year 1632, when the Daimyo of the 小笠原 Ogasawara clan became regent, he had the shrine repaired and venerated again.

This unusual shrine is on the island of Ikitsuki near Hirado, Kyushu.
Named Hokura Suitengu, it has strong kappa associations.
According to local tradition, the small pond was build by 99 kappa from a mixture of sea and mountain water, and to secure it from storms they built up the sides with rocks. Later the kappa morphed into a large unagi eel (「神うなぎ」) which is treated as divine. If locals spot it when coming to worship, they feel they will be specially blessed... . Dougill John on facebook .

Nor are the dead the only invisible powers which are dreaded at the time of the Hotoke-umi. There are the most powerful ma and the kappa. At all times the swimmer fears the kappa, the Ape of the Waters, hideous and obscene, who reaches up from the depths to draw men down and to devour their entrails. Only their entrails.

- Author’s Footnote:
The kappa is not really a sea goblin, but a river goblin, and haunts the sea only in the area of the mouths of rivers.
About a mile and a half from Matsue, at the little village of Kawachimura, on the river called Kawachi, stands a little temple called Kawako-no-miya, or the Miya of the Kappa.
(In Izumo, among the common people, the word kappa is not used, but the term kawako, or “The Child of the River.”)
A document said to have been signed by a kappa is preserved in this little shrine. The story goes that in ancient times, the kappa living in the Kawachi used to seize and destroy many of the inhabitants of the village and many domestic animals. One day, however, while trying to seize a horse that had entered the river to drink, the kappa got its head twisted in some way under the belly-band of the horse, and the terrified animal, rushing out of the water, dragged the kappa into a field. There, the owner of the horse and a number of peasants seized and bound the kappa.
All the villagers gathered to see the monster, which bowed its head to the ground and audibly begged for mercy.

The peasants wanted to kill the goblin at once; however, the owner of the horse, who happened to be the head man of the mura (village), said, “It is better to make it swear never again to touch any person or animal belonging to Kawachimura.” A written form of oath was prepared and read to the kappa. It said that it could not write, but that it would sign the paper by dipping its hand in ink, and pressing the imprint at the bottom of the document. This having been agreed to and done, the kappa was set free. From that time forward, no inhabitant or animal of Kawachimura was ever assaulted by the goblin. source : books.google.co.jp

. yakuyoke 厄除け amulets to ward off evil .
- kappa yoke, kappayoke 河童除け to ward off the evil influence of a kappa, especially water accidents.
mizuyoke 水難除け amulets to ward off water accidents
They are also sold at temples.

- quote - The Mysterious Kappa Shrine
The shrine was inside of what seemed like three huge boulders placed together to form a cave.

Inside the cave was a statue of a male and female Kappa. The male was holding his willy while the female looked on in a seated position. They both have a wide eyed blank gaze that was weirdly disturbing. Almost as if the minute you walked into the shrine you stumbled upon the two just finishing up some sexcapade and they got scared and turned to stone.- source : www.great-sensei.com